Camera module

ABSTRACT

A camera module may comprise: a printed circuit board on which an image sensor is mounted; a holder member disposed above the printed circuit board and having a plurality of magnets installed thereon; a bobbin installed on the inside of the holder member to be capable of moving along an optical axis, and having a coil unit installed on the outer peripheral surface thereof to be capable of electrically interacting with the magnets; a plurality of receptacles formed in the peripheral surface of the bobbin to form spaces that are separated from the coil unit; and a cover member having a plurality of integrally formed inner yokes, which are formed at positions corresponding to the plurality of receptacles and have a surface on one side thereof separated a certain distance from the coil unit and a surface on the other side thereof separated a certain distance from the bobbin.

CROSS-REFERENCE TO RELATED APPLICATION

This application is the U.S. national stage application of InternationalPatent Application No. PCT/KR2014/006238, filed Jul. 11, 2014, whichclaims priority to Korean Application No. 10-2013-0081956, filed Jul.12, 2013, the disclosures of each of which are incorporated herein byreference in their entirety.

BACKGROUND

Field of the Disclosure

The present disclosure relates to a camera module.

Discussion of the Related Art

A camera module may include an image sensor, an infrared cut-off filterconfigured to block light in infrared area from being incident on theimage sensor, and an optical system formed of at least one lensconfigured to deliver an image to the image sensor.

Here, the optical system may be installed with an actuator moduleconfigured to perform auto focusing function and handshake compensationfunction.

The actuator module may be composed in various ways. In general, a voicecoil motor is commonly used. The voice coil motor is driven byelectromagnetic interaction between magnets fixed at a holder member anda coil unit wound on an outer circumferential surface of a bobbin, andmay perform auto focusing function.

Generally, a yoke made of a major material of iron (Fe) that is aferromagnetic body is provided in order to form a magnetic path of themagnet. Recently, a voice coil motor, without any separate yokeinstalled thereat, having an inner yoke integrally formed with a covermember such as a shield can made of iron (Fe) that is a ferromagneticbody at a position at which the yoke is to be installed, is also beingdeveloped.

Such voice coil motor having an inner yoke is advantageous in that theassembly of the camera module becomes convenient and the number ofcomponents can be reduced. However, when the length of the inner yoke istoo short, the electromagnetic efficiency declines, an interference withan upper portion of the coil unit wound on an outer circumferentialsurface of the bobbin may occur during being driven, and foreignmaterials may be introduced.

In addition, when the length of the inner yoke is too long, theelectromagnetic efficiency declines, as well as the verticality andconcentricity becomes difficult to manage, thereby the manufacturabilityis degraded.

SUMMARY OF THE DISCLOSURE

According to an exemplary embodiment of the present disclosure, a cameramodule having an advanced structure so as to prevent introduction offoreign materials is provided, in consideration of the electromagneticattribute.

In a general aspect of the present disclosure, there is provided acamera module, the camera module comprising: a PCB (Printed CircuitBoard); a holder member arranged at an upper side of the PCB andinstalled with a plurality of magnets; a bobbin movably installed at aninner side of the holder member and installed with a coil unit facingthe magnet at an outer circumferential surface of the bobbin; aplurality of accommodation grooves formed at a circumferential surfaceof the bobbin and being spaced from the coil unit at a predeterminedinterval to form a spaced portion; and a cover member integrally formedwith a plurality of inner yokes formed by being bent at a positioncorresponding to that of the plurality of accommodation grooves, whereinone side surface of the inner yoke is spaced from the coil unit at apredetermined interval and another side surface of the inner yoke isspaced from the bobbin at a predetermined interval.

In some exemplary embodiments of the present disclosure, each of theinner yoke and the accommodation groove is formed at four edge portionsof the cover member and the holder member, respectively.

In some exemplary embodiments of the present disclosure, the inner yokemay include: a connection portion connected to an upper portion of thecover member and formed by being bent in a round shape; and a pair ofescape grooves symmetrically formed at a position adjacent to that ofthe connection portion.

In some exemplary embodiments of the present disclosure, the escapegroove may have a length (L1) of 20-50% of an entire length (L2).

In some exemplary embodiments of the present disclosure, the escapegroove may include a slanted surface having a predetermined angle.

In some exemplary embodiments of the present disclosure, an entirelength (L2) of the inner yoke may be formed to be longer than a length(H1) from an upper surface of the cover member to an upper surface ofthe coil unit.

In some exemplary embodiments of the present disclosure, an entirelength (L2) of the inner yoke may be 20-40% of an entire length (H) ofthe magnet.

In some exemplary embodiments of the present disclosure, a length (H2)of an end of the inner yoke overlapped with the coil unit by beinginserted in the accommodation groove may be formed to be longer than abackstroke distance of the bobbin.

In some exemplary embodiments of the present disclosure, a surface ofthe inner yoke facing the bobbin may have a curvature corresponding tothat of a virtual circle (a) concentric with the bobbin.

In some exemplary embodiments of the present disclosure, a surface ofthe inner yoke facing the bobbin may be provided in a flat and straightshape, and the inner yokes facing each other may be mutually parallel.

In some exemplary embodiments of the present disclosure, an angle (α)formed by the surface of the inner yoke facing the bobbin and a lateralsurface of the cover member may be 45 degrees.

In some exemplary embodiments of the present disclosure, the holdermember may include a plurality of magnet installation holes at foursurfaces thereof for magnets of a same size to be inserted.

In some exemplary embodiments of the present disclosure, the covermember may be formed of a ferromagnetic body.

In some exemplary embodiments of the present disclosure, the bobbin mayinclude a lens barrel installed inside with at least one lens.

In some exemplary embodiments of the present disclosure, the cameramodule may comprise: upper and lower elastic members respectively fixedat upper and lower portions of the holder member to elastically supportupward and downward motions of the bobbin.

In some exemplary embodiments of the present disclosure, the coil unitmay be a ring-shaped coil block coupled by being inserted in an outercircumferential surface of the bobbin.

In some exemplary embodiments of the present disclosure, the coil unitmay include: a straight surface arranged at a position corresponding tothat of the magnet; and a curved surface arranged at a positioncorresponding to that of the inner yoke and the accommodation groove.

In some exemplary embodiments of the present disclosure, the bobbin mayinclude: a first surface flatly formed at a surface corresponding to thestraight surface; and a second surface roundly formed at a surfacecorresponding the curved surface.

In some exemplary embodiments of the present disclosure, the firstsurface may include: a protruded portion preventing the coil unit fromdeparting in an optical axis direction.

In some exemplary embodiments of the present disclosure, the cameramodule may comprise: a base interposed between the PCB and the holdermember and installed with an infrared cut-off filter.

According to an exemplary embodiment of the present disclosure, aninterference between the inner yoke and the bobbin occurring when theauto focusing operation is being performed or a shaking of the bobbinoccurs due to an external impact may be minimized, because an escapegroove is formed at the inner yoke.

In addition, according to an exemplary embodiment of the presentdisclosure, foreign materials generated by motions of the bobbin orflowing down along the inner yoke may be collected by the groovedportion, because an end of the inner yoke is inserted in a groovedportion formed in an internal spaced portion of the coil unit wound onan outer circumferential surface of the bobbin.

In addition, according to an exemplary embodiment of the presentdisclosure, the voice coil motor may have optimal electromagneticcharacteristic, because an entire length of the inner yoke is formed tobe more than 20% of an entire length of the magnet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating an example of a camera moduleaccording to an exemplary embodiment of the present disclosure.

FIG. 2 is an exploded perspective view of FIG. 1.

FIG. 3 is an enlarged view illustrating portion A of FIG. 2.

FIG. 4 is a B-B sectional view of FIG. 1.

FIG. 5 is an enlarged view illustrating portion C of FIG. 4.

FIG. 6 is a plan view illustrating a cover member having an inner yokeaccording to a first exemplary embodiment of the present disclosure.

FIG. 7 is a plan view illustrating a cover member having an inner yokeaccording to a second exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, an exemplary embodiment of the present disclosure will bedescribed with reference to the drawings.

FIG. 1 is a perspective view illustrating an example of a camera moduleaccording to an exemplary embodiment of the present disclosure; FIG. 2is an exploded perspective view of FIG. 1; FIG. 3 is an enlarged viewillustrating portion A of FIG. 2; FIG. 4 is a B-B sectional view of FIG.1; FIG. 5 is an enlarged view illustrating portion C of FIG. 4; FIG. 6is a plan view illustrating a cover member having an inner yokeaccording to a first exemplary embodiment of the present disclosure; andFIG. 7 is a plan view illustrating a cover member having an inner yokeaccording to a second exemplary embodiment of the present disclosure.

As illustrated in FIGS. 1 and 2, a camera module according to anexemplary embodiment of the present disclosure may include a PCB(Printed Circuit Board) (10), a base (20), a holder member (30), abobbin (40) and a cover member (50).

An image sensor (11) may be mounted at the PCB (10). The PCB (10) mayform a bottom surface of the camera module. The image sensor (11) may bemounted at a center of an upper surface of the PCB (10), so as to bedisposed with at least one lens (not illustrated) accommodated in thelens barrel (42) along an optical axis direction. The image sensor mayconvert an optical signal of an object that has been incident throughthe lens to an electrical signal.

The base (20) may include an infrared cut-off filter (25) installed at aposition corresponding to that of the image sensor (11). In such case,the infrared cut-off filter (25) may be installed at a through-holeformed at a center of the based (20). Alternatively, a blue filter maybe provided instead of the infrared cut-off filter. Here, the infraredcut-off filter (25) may be formed of, for example, a film material or aglass material. In addition, an infrared cut-off coating material may bearranged on a flat optical filter such as a cover glass for image planeprotection, cover glass, etc.

A lower portion of the base (20) may be connected to the PCB (10), andan upper portion of the base (20) may support a bottom surface of theholder member (30) (to be described hereinafter). The base (20) mayinclude a separate terminal member in order for electrical connectionwith the PCB (10). The terminal member may be provided as a separatemember. Alternatively, the terminal member may be provided as a surfaceelectrode formed on a surface of the base (20).

In addition, the base (20) may include at a lateral surface thereof anaccommodation groove (21) to accommodate a terminal portion (notillustrated) electrically connected to the lower elastic member (45) orthe coil unit (42). The terminal portion may be formed by beingintroduced at a lateral surface of the lower elastic member (45). Inaddition, the accommodation groove (21) may gradually form a right angleor an acute angel along a downward direction, so as to correspond to abent angle of the terminal portion.

In addition, the base (20) may include at least one fixing protrusion(22) formed by being protruded at an upper edge of the base (20) to havea surface-to-surface contact with or be coupled to an internal lateralsurface of the cover member (50). The fixing protrusion (22) may guidethe cover member (50) to be readily coupled as well as may facilitateconcrete fixation after the coupling.

In addition, a recessed portion (23) may be formed by being recessed ata center of the base (20) so that the bobbin (210) can be disposed bybeing spaced.

In addition, the base (20) is not an essential structure for the presentdisclosure. Therefore, although not illustrated in the drawings, theholder member (30) may be configured to perform a function of the base(20).

The holder member (30) may be formed in a broadly quadrangular shape,and may include a plurality of magnet installation holes (32) at each offour surfaces of the holder member (30), so that a plurality of magnets(33) can be installed at the magnet installation holes (32). Asillustrated in the drawings, the magnet installation hole (32) may beformed at a lateral surface of the holder member (30). Alternatively,the magnet installation hole (32) may be formed at each edge of theholder member (30). In addition, the holder member (30) may be formed ofan insulated material, and may be implemented as an injection moldingmaterial, in consideration of productivity.

In addition, at least two stoppers (37) that are protruded so as toabsorb impact energy of external impacts may be formed at an upperlateral surface of the holder member (30) by being spaced at apredetermined interval. The stopper (37) may be integrally formed withthe holder member (30), or may be formed at the bobbin (40).Alternatively, the stopper (37) may not be formed at all.

In addition, the holder member (30) may be formed in a shapecorresponding to that of an inner lateral surface of the cover member(50). Otherwise, the holder member (30) may form an external appearanceof the lens actuating unit by being integrally formed with the covermember (50), without being separately provided.

Each of the magnets (33) may be formed in a size corresponding to eachother. In addition, the magnets (33) facing each other may be arrangedin mutual parallel position.

As illustrated in FIG. 2, the holder member (30) may be provided in ahexahedron shape, with its four surfaces formed in shapes of thinframes. In addition, upper and lower elastic members (44)(45) may berespectively installed at upper and lower portions of the holder member(30) to elastically support upward and downward motions of the bobbin(40) in an optical axis direction.

According to an exemplary embodiment of the present disclosure, a bottomsurface of the holder member (30) may be coupled to the base (20), andan upper surface of the holder member (30) may be coupled to the covermember (50) (to be described hereinafter) at a fixed position. Here, theupper elastic member (44) may be interposed between the holder member(30) and the cover member (50), and the lower elastic member (45) may beinterposed between the holder member (30) and the base (20).

The bobbin (40) may be installed in the internal space of the holdermember (30) so as to be movable reciprocatingly in a direction parallelto the optical axis. The bobbin (40) may be installed with a coil unit(43) at an outer circumferential surface of the bobbin (40) so as toenable electromagnetic interaction with the magnet (33).

The bobbin (40) may include a lens barrel (42) installed inside with atleast one lens (42 a). As illustrated in FIG. 2, the lens barrel (42)may be formed to be capable of being screw-coupled to an internal sideof the bobbin (40). However, the present disclosure is not limitedhereto. Although not illustrated in the drawings, the lens barrel (42)may be directly coupled to the internal side of the bobbin (40) by meanssuch as gluing except the screw coupling. Otherwise, the at least onelens (42 a) may be integrally formed with the bobbin (40) without thelens barrel (42). The lens (42 a) may be formed of a single lens, or maybe composed of a plurality of lenses to form an optical system.

The bobbin (40) may be installed, at upper and lower portions thereof,with the upper and lower elastic members (44) (45), respectively. Eachof the upper and lower elastic members (44) (45) may have one endthereof connected to the holder member (30) and another end thereofconnected to the bobbin (40), respectively.

For example, as illustrated in FIG. 2, first and second protrusions (34a) (35 a) for coupling the elastic members may be respectively formed atupper and lower portions of the holder member (30), and first and secondprotrusion accommodation hole (44 a) (45 a) may be respectively formedat positions corresponding to those of the first and second elasticmembers (44) (45), so that the upper and lower elastic members (44) (45)may be coupled to the holder member (30) via coupling of thoseprotrusions and protrusion accommodation holes. In the same manner, theupper and lower elastic members (44) (45) may be coupled to the upperand lower portions of the bobbin (40) via such structure as described inthe above.

According to such structure as described in the above, the upper andlower elastic member (44) (45) may elastically support the bobbin (40)while performing cantilever action with a fixed position of the holdermember (30) as an axis, when the bobbin (40) performs reciprocatingmotions with respect to the optical axis direction.

Meanwhile, the coil unit (43) may be directly wound on an outercircumferential surface of the bobbin (40). Alternatively, the coil unit(43) may be provided as a ring-shaped coil block coupled by beinginserted in an outer circumferential surface of the bobbin (40), asillustrated in FIG. 2. The coil unit (43) formed as a coil block mayinclude a straight surface (43 a) arranged at a position correspondingto that of the magnet (33) and a curved surface (43 b) arranged at aposition corresponding to that of the inner yoke (100) and theaccommodation groove (200).

In addition, the bobbin (40) may include a first surface (40 a) flatlyformed at a surface corresponding to the straight surface (43 a) and asecond surface (40 b) roundly formed at a surface corresponding thecurved surface (43 b), so that the coil unit (43) can be coupled to anouter circumferential surface of the bobbin (40). Here, the firstsurface (40 a) may include a protruded portion (47) preventing the coilunit (43) from departing in an optical axis direction, so as to preventthe coil unit (43) from being departed from the installation positiondue to external impacts such as an impact that occur during thereciprocating motions of the bobbin (40).

In addition, the bobbin (40) may include a plurality of accommodationgrooves (200) formed at a circumferential surface of the bobbin (40) andbeing spaced from the coil unit (43) at a predetermined interval to forma spaced portion. The inner yoke (100) formed at the cover member (50)may be inserted in the accommodation groove (200). The relationshipbetween the inner yoke (100) and the accommodation groove (200) will behereinafter described again.

The cover member (50) may be formed of a ferromagnetic body such as aniron, may be provided in a shape corresponding to that of the holdermember (30), so as to cover the holder member (30). That is, asillustrated in FIGS. 1 to 4, when the holder member (30) is in atetragonal shape, the cover member (50) may be also provided in atetragonal shape.

The cover member (50) may be integrally formed with a plurality of inneryokes (100) formed at a position corresponding to that of the pluralityof accommodation grooves (200). According to an exemplary embodiment ofthe present disclosure, one side surface of the inner yoke (100) may bespaced from the coil unit (43) at a predetermined interval, and anotherside surface of the inner yoke (100) may be spaced from the bobbin (40)at a predetermined interval. In addition, each of the inner yoke (100)and the accommodation groove (200) may be formed at four edge portionsof the cover member (50) and the holder member (30), respectively.

As illustrated in FIGS. 2 and 3, the inner yoke (100) may be formed bybeing bent from an upper surface of the cover member (50) to an internalside in a direction parallel to the optical axis. A connection portionbetween the cover member (50) and the inner yoke (100) may be formed ina round shape, a slanted shape or a rectangularly bent shape.

The inner yoke (100) may include a pair of escape grooves (110)symmetrically formed at a position adjacent to that of the connectionportion. The portion where the escape groove (110) is formed may form abottleneck section. The bottleneck section where the escape groove (110)is formed may minimize interference between the inner yoke (100) and thebobbin (40) occurring when the bobbin (40) is being driven.

As illustrated in FIG. 3, a length (L1) of the escape groove (110) maybe of 20-50% of an entire length (L2) of the inner yoke (100). Theescape groove (110) may include a slanted surface (111) having apredetermined angle.

Due to forming of the slanted surface (111), the inner yoke (100) mayhave a width gradually being widened as approaching an end portion ofthe inner yoke (100). Here, a width of the end portion of the inner yoke(100) may be formed to be corresponding to a width of the accommodationgroove (200), or may formed to be narrower than the width of theaccommodation groove (200).

As illustrated in FIG. 3, the escape groove (110) may have a cuttingwidth (w) in 0.1-0.5 mm with respect to a width direction of the inneryoke (100). However, the above numerical values are intended to beillustrative, and the present disclosure is not limited hereto.Therefore, the cutting width of the escape groove (110) may be modifiedaccording to variation in size of the camera module.

Referring to FIGS. 3 to 5, an entire length (L2) of the inner yoke (100)may be formed to be longer than a length (H1) from an upper surface ofthe cover member (30) to an upper surface of the coil unit (43).According to such structure, the inner yoke (100) may be inserted intoan internal space of the accommodation groove (200), and may be arrangedto be overlapped with the coil unit (43) at a predetermined lengthinside of the spaced portion formed between the coil unit (43) and thebobbin (40).

In addition, an entire length (L2) of the inner yoke may be provided tobe 20-40% of an entire length (H) of the magnet (33). This is because,if the entire length (L2) of the inner yoke (100) is too short beyondthe above-mentioned range, the electromagnetic efficiency declines, aninterference with an upper portion of the coil unit (43) may occurduring being driven, and foreign materials may be introduced in the gaptherebetween. In addition, if the length (L2) of the inner yoke (100) istoo long, the electromagnetic efficiency also declines, as well as theverticality and concentricity becomes difficult to manage, thereby themanufacturability is degraded.

In addition, a length (H2) of an end of the inner yoke (100) overlappedwith the coil unit (43) by being inserted in the accommodation groove(200) may be formed to be longer than a backstroke distance of thebobbin (40). In such case, an upper end portion of the coil unit (43)may be arranged upper than the end of the inner yoke (100) at the lowestposition during the reciprocating motions of the bobbin (40).

In addition, the end of the inner yoke (100) may be arranged, at thereference position, by being spaced from a bottom surface of theaccommodation groove (200) at a predetermined interval. This is to avoidcontact and interference between the end of the inner yoke (100) and thebottom surface of the accommodation groove (200) at the highest positionduring the reciprocating motions of the bobbin (40).

According to a first exemplary embodiment, as illustrated in FIG. 6, asurface of the inner yoke (100) facing the bobbin (40) may have acurvature corresponding to that of a virtual circle (a) concentric withthe bobbin (40).

According to a second exemplary embodiment, a surface of the inner yoke(100) facing the bobbin (40) may be provided in a flat and straightshape, and the inner yokes (100) facing each other may be mutuallyparallel. Here, an angle (α) formed by the surface of the inner yoke(100) facing the bobbin (40) and a lateral surface of the cover member(50) may be 45 degrees.

As described in the above, the inner yoke (100) integrally formed withthe cover member (50) may be arranged at an internal side of the spacedportion formed by the accommodation groove (200) formed at an outercircumferential surface of the bobbin (40). Thereby, as illustrated inFIGS. 4 and 5, a structure to primarily collect foreign materialsflowing down along the inner yoke (100) may be provided, so as tominimize introduction of foreign materials in the camera module.

In addition, an entire length (L2) of the inner yoke (100) may be formedto be 20-50% of an entire length (H) of the magnet (33), while theentire length (L2) of the inner yoke (100) may be formed to be longerthan a length (H1) from an upper surface of the cover member (30) to anupper surface of the coil unit (43). Thereby, the electromagneticefficiency of the camera module may be maximized, as well as theinterference between each of components during upward and downwardmotions of the bobbin (40) may be minimized.

In addition, motions of both wing portions of the inner yoke (100) maybe restricted in the spaced portion formed by an inner circumferentialsurface of the accommodation groove (200) and a surface of the coil unit(43) facing the bobbin (40). Thereby, the bobbin (40) may be preventedfrom rotating with respect to the optical axis direction due to anexternal impact or a malfunction, etc.

The abovementioned exemplary embodiments are intended to beillustrative, and not to limit the scope of the claims. Manyalternatives, modifications, variations, and equivalents will beapparent to those skilled in the art. The features, structures, methods,and other characteristics of the exemplary embodiments described hereinmay be combined in various ways to obtain additional and/or alternativeexemplary embodiments within an equivalent scope. Therefore, thetechnical scope of the rights for the present disclosure shall bedecided by the appended claims and equivalents thereof.

What is claimed is:
 1. A voice coil motor comprising: a cover member; a holder member disposed in the cover member; a bobbin disposed in the holder member and configured to move in a direction of an optical axis; a coil disposed on an outer lateral surface of the bobbin; a magnet disposed on the holder member and facing the coil; a base disposed below the bobbin; and an upper elastic member disposed in the cover member and comprising an inner portion coupled with an upper portion of the bobbin, an outer portion coupled with an upper portion of the holder member, and a middle portion connecting the outer portion and the inner portion of the upper elastic member; wherein the bobbin comprises a groove disposed on the outer lateral surface of the bobbin and forming a space between the bobbin and the coil, wherein the cover member comprises an upper wall formed with a hole, a lateral wall extending downward from the upper wall of the cover member, and an inner yoke extending downward from the upper wall of the cover member and disposed inside the lateral wall of the cover member; wherein at least a portion of the inner yoke is disposed in the space between the bobbin and the coil, wherein the inner yoke comprises a first portion, a second portion disposed below the first portion, and a third portion connecting the first portion and the second portion and disposed between the first portion and the second portion; wherein a horizontal width of the first portion of the inner yoke is shorter than a horizontal width of the second portion of the inner yoke, wherein the groove of the bobbin comprises a shape corresponding to a shape of the second portion of the inner yoke, wherein at least a portion of the second portion of the inner yoke is disposed in the groove, wherein the lateral wall of the cover member comprises a first lateral wall, a second lateral wall opposite to the first lateral wall, a third lateral wall and a fourth lateral wall disposed between the first lateral wall and the second lateral wall and being opposite to each other, wherein the holder member comprises a first pillar portion disposed on a first corner of the cover member between the first lateral wall and the third lateral wall, a second pillar portion disposed on a second corner of the cover member between the first lateral wall and the fourth lateral wall, a third pillar portion disposed on a third corner of the cover member between the second lateral wall and the third lateral wall, and a fourth pillar portion disposed on a fourth corner of the cover member between the second lateral wall and the fourth lateral wall, wherein the magnet comprises a first magnet disposed between the first pillar portion and the second pillar portion, and a second magnet disposed between the third pillar portion and the fourth pillar portion, wherein the first magnet is disposed at a position facing and corresponding to the first lateral wall and the second magnet is disposed at a position facing and corresponding to the second lateral wall, and wherein the first portion of the inner yoke is overlapped with a portion of the upper elastic member in a direction perpendicular to the direction of the optical axis.
 2. The voice coil motor of claim 1, wherein the inner yoke comprises four inner yokes, and the groove of the bobbin comprises four grooves; wherein each of the four inner yokes are disposed at a position corresponding to each of four corner portions of the cover member, wherein each of the four grooves is disposed at a position corresponding to each of the four inner yokes, and wherein the first magnet is disposed between the coil and the first lateral wall, and the second magnet is disposed between the coil and the second lateral wall.
 3. The voice coil motor of claim 1, wherein the inner yoke further comprises: a connection portion connecting the upper wall of the cover member and the first portion of the inner yoke, and wherein the connection portion is formed in any one of a round shape, a slanted shape, and a rectangularly bent shape.
 4. The voice coil motor of claim 1, wherein a sum of the first portion and the third portion has a length (L1) of 20-50% of an entire length (L2) of the inner yoke in the direction of the optical axis.
 5. The voice coil motor of claim 1, wherein a horizontal width of the third portion gradually increases from the first portion to the second portion.
 6. The voice coil motor of claim 1, wherein an entire length (L2) of the inner yoke is longer than a length (H1) from the upper wall of the cover member to an upper surface of the coil in the direction of the optical axis, and wherein the entire length (L2) of the inner yoke is 20-40% of an entire length (H) of the magnet in the direction of the optical axis.
 7. The voice coil motor of claim 1, wherein a top end of the coil is disposed higher than a bottom end of the inner yoke at the lowest position of the bobbin.
 8. The voice coil motor of claim 1, wherein a surface of the inner yoke facing the coil comprises a curvature corresponding to that of the coil or a flat surface.
 9. The voice coil motor of claim 8, wherein an angle (α) between an imaginary surface extending from the surface of the inner yoke facing the coil and a surface of the lateral wall of the cover member meeting with the imaginary surface is an angle of 45 degrees.
 10. The voice coil motor of claim 1, wherein the cover member comprises a ferromagnetic substance.
 11. The voice coil motor of claim 1, further comprising: a lower elastic member coupled with a lower portion of the bobbin, and wherein the coil has an octagonal shape, and wherein at least a portion of the first portion of the inner yoke is disposed at a position higher than an upper surface of the magnet.
 12. The voice coil motor of claim 1, wherein the coil comprises: a flat surface disposed at a position corresponding to that of the magnet, and a curved surface disposed at a position corresponding to that of the inner yoke, and wherein the bobbin comprises a flat surface disposed at a position corresponding to the flat surface of the coil and a curved surface disposed at a position corresponding the curved surface of the coil.
 13. The voice coil motor of claim 5, wherein an angle between a lateral side of the first portion and a lateral side of the third portion meeting with the lateral side of the first portion forms an obtuse angle.
 14. The voice coil motor of claim 1, wherein two grooves are defined by the first portion, the second portion, and the third portion of the inner yoke and the upper wall of the cover member; and wherein the two grooves of the inner yoke are symmetrically formed on both lateral sides of the inner yoke.
 15. The voice coil motor of claim 1, wherein the horizontal width of the second portion of the inner yoke is shorter than a horizontal width of the groove of the bobbin or is corresponding to the horizontal width of the groove of the bobbin.
 16. The voice coil motor of claim 1, wherein the second portion of the inner yoke is disposed in the groove of the bobbin such that the bobbin is configured to be inhibited from rotating with respect to the direction of the optical axis.
 17. A camera module comprising: the voice coil motor of claim 1; a lens coupled to the bobbin of the voice coil motor; a printed circuit board disposed below the base of the voice coil motor; and an image sensor coupled to the printed circuit board.
 18. The voice coil motor of claim 1, wherein the upper portion of the holder member is disposed between the magnet and the upper wall of the cover member, and wherein the outer portion of the upper elastic member is disposed on an upper surface of the upper portion of the holder member.
 19. A voice coil motor comprising: a cover member comprising an upper wall formed with a hole, a lateral wall extending downward from the upper wall of the cover member, and an inner yoke extending downward from the upper wall of the cover member and disposed inside the lateral wall of the cover member; a bobbin disposed in the cover member and configured to move in a direction of an optical axis; a coil disposed on an outer lateral surface of the bobbin; a magnet facing the coil and disposed between the cover member and the bobbin; a base disposed below the bobbin and coupled with the lateral wall of the cover member; and an upper elastic member disposed in the cover member and comprising an inner portion coupled with the bobbin, an outer portion disposed on an outside of the inner portion, and a middle portion connecting the outer portion and the inner portion of the upper elastic member; wherein the bobbin comprises a groove disposed on the outer lateral surface of the bobbin and forming a space between the bobbin and the coil, wherein at least a portion of the inner yoke is disposed in the space between the bobbin and the coil, wherein the inner yoke comprises a first portion contacting with the upper wall of the cover member, a second portion disposed below the first portion, and a third portion connecting the first portion and the second portion and disposed between the first portion and the second portion; wherein a horizontal width of the first portion of the inner yoke is shorter than a horizontal width of the second portion of the inner yoke, wherein the groove of the bobbin comprises a shape corresponding to a shape of the second portion of the inner yoke, wherein at least a portion of the second portion of the inner yoke is disposed in the groove, wherein the lateral wall of the cover member comprises a first lateral wall, a second lateral wall opposite to the first lateral wall, a third lateral wall and a fourth lateral wall disposed between the first lateral wall and the second lateral wall and being opposite to each other, wherein the holder member comprises a first pillar portion disposed on a first corner of the cover member between the first lateral wall and the third lateral wall, a second pillar portion disposed on a second corner of the cover member between the first lateral wall and the fourth lateral wall, a third pillar portion disposed on a third corner of the cover member between the second lateral wall and the third lateral wall, and a fourth pillar portion disposed on a fourth corner of the cover member between the second lateral wall and the fourth lateral wall, wherein the magnet comprises a first magnet disposed between the first pillar portion and the second pillar portion, and a second magnet disposed between the third pillar portion and the fourth pillar portion, wherein the first magnet is disposed at a position facing and corresponding to the first lateral wall and the second magnet is disposed at a position facing and corresponding to the second lateral wall, and wherein at least a portion of the first portion of the inner yoke is disposed at a position higher than an upper surface of the magnet.
 20. The voice coil motor of claim 19, wherein the magnet is spaced apart from the upper wall of the cover member, wherein the outer portion of the upper elastic member is disposed between the magnet and the upper wall of the cover member, and wherein the first portion of the inner yoke is overlapped with a portion of the upper elastic member in a direction perpendicular to the direction of the optical axis. 